It is known to provide a waterproof shoe with a water permeable and water vapor permeable upper portion, an insole which is sewn to the upper portion thus providing a seam, and an inner functional material layer which is arranged on the inside of the upper portion which is a laminate of a waterproof, water vapor permeable layer and a textile layer at least on one side of the permeable layer, wherein the insole, the lower edge of the upper portion facing the insole and the lower edge of the functional material layer facing the insole are located within an injection molded plastic sole.
The advantage of a shoe of such a construction is that it is not only waterproof but also breathable, i.e. passes water vapor. If the shoe is exposed to water from outside, the water cannot reach the foot. On the other hand, in contrast to waterproof shoes with a waterproof and water-vapor impermeable outer material, e.g. rubber boots, foot perspiration can escape through the water and water vapor permeable upper material.
Seams through the functional material layer portions create difficulties with respect to waterproofness. To overcome these difficulties, some prior art methods use sock-like functional layer inserts between the foot and the outsole or insole on the one hand and the inner lining of the shoe on the other hand. Since the desired shape can be imparted to such a sock-like insert by heat sealing, it does not contain any seam holes. This method, however, is very expensive to manufacture since the sock-like inserts must be adapted to the shoe shape.
A shoe designed as described above is disclosed in EP 02 98 360 B1. In this case the insole edge, the lower edge of the functional material layer and the lower edge of the upper material are sewn together by a single seam. To prevent water from creeping down the upper up to this connection seam and along the connection seam through the seam holes in the functional material layer to the inside of the shoe, the lower area of the upper material in this shoe consists of a mesh band which is not water conductive. The lower edge of the mesh band is sewn to the insole and the lower edge of the functional material layer by the already mentioned seam. The upper edge of the mesh band is sewn only to the remaining part of the upper material, but not to the functional material layer. Water creeping down the upper material can thus not reach the seam going through the edge of the functional material layer.
This design overcomes another problem. The functional material layer is a laminate that incorporates a textile layer, at least on its inside facing away from the upper material, generally in the form of a textile lining. When the functional material layer laminate is cut to size, it is virtually inevitable that little textile threads are laid bare around the cut edge of the functional material towards its outside. These textile threads act as water bridges when water reaches the cut edge on the outside of the functional material layer. Through the use of the monofilic mesh band, however, water cannot reach the cut edge of the functional material layer so that the water bridge function of such threads cannot have any effect. This method results in a very high reliability of the waterproofness of such waterproof, breathable shoes which are not equipped with a closed, sock-like functional layer insert. The mesh band, however, presents difficulty in handling, in particular in small shoes, such as children's shoes, if wrinkles in the mesh are to be avoided, in particular at areas where the shoe contours are very curved. These difficulties are eased by a shoe as described in DE 41 38 836 A1. In this shoe, as in the shoe known from EP 02 98 360 B1, the upper material edge is cut slightly shorter than the functional material edge, but the gap between the upper material edge and the functional material edge is not closed by a meshband but left completely open, i.e. it is only the lower edge of the functional material layer that is sewn to the insole edge. The lower edge of the upper material ends at a certain distance from the lower edge of the functional material layer. The lower edge of the upper material is glued to the functional material layer to prevent through holes of a seam from piercing the functional material. The gap between the upper material edge and the insole seam is closed by the injection molded outsole.
This approach, too, results in highly reliable waterproofness of breathable shoes. However, quite a high degree of dexterity is required to produce such a shoe.
Since in both state of the art approaches the lower edge of the upper material of the upper material itself ends somewhat above the insole seam, the injection molded outsole must have a relatively high lateral wall to prevent the lower edge of the upper material leg edge or the mesh band from lying open.